SP8612B 1.8GHz Counter

Divide-by-Four 1800 MHz Counter

SP8612 1.8GHz Counter Plessey


  • ECL Compatible Outputs
  • AC Coupled Input (internal bias)
  • Typical Operating Frequency 2GHz

Quick Reference Data

  • Supply Voltage: -6.8V
  • Power Consumption: 600mW
  • Output Voltage Swing: 750mV typ.


The SP8612B is an asynchronous emitter coupled logic counter which provides ECL 10K compatible outputs and can drive 100-ohm lines. It operates from a 6.8V supply or split supplies of +5V and -1.8V. Otherwise, it is similar to the SP8610/11.

Operating Note

  1. The clock input (pin 4) should be capacitively coupled to the signal source. The input signal path is completed by connecting a capacitor from the internal bias decoupling, pin 6 to ground.
  2. If no signal is present the device self-oscillate; if this is undesirable, it may be prevented by connecting a 10k resistor from the input to Vee (i.e. pin 4 to pin 7); this reduces sensitivity by approximately 100mV.
  3. The input can operate at very low frequencies, but slew rate must be better than 200V/µs.
  4. The input impedance of the SP8612 is a function of frequency
  5. The emitter follower outputs require external load resistors. These should not be less than 330 ohms, and a value of 620 ohms is recommended.
  6. These devices may be used with split supply lines employing the circuit of Fig. 6. Some improvement in the upper frequency of operation may be obtained under these conditions, but suitable circuit layout must be employed to achieve this improvement.